Dose-response relationships toxic effects spectrum

Stratification of lead s toxicity in humans into diagnosable disease or probabilistic risks of disease is not simply defined by where exposures and toxic effects align across the full spectrum of lead s dose—response relationships. That is, one cannot infer that only historic clinical effects at high Pb exposures comprise diagnosable disease and that subclinical effects always require population or epidemiological approaches. See the historical scientific perspective on these topics by Mushak (1992). 

A recent text illustrates the first example. The text reads "The relationship between exposure and the spectrum of effects is referred to as the "dose-response" and an understanding of this relationship constitutes a basis for the study of toxicity. By animal experimentation, dose-response curves have been developed for many chemicals, permitting the development of acceptable daily intakes (ADI) based on... 

In brief, this relationship indicates that as dose increases above some threshold, effects get worse and more effects occur. This relationship has been a dictum of toxicology for centuries and still apphes across the whole dose—response spectrum for lead. Presented here is the chronology of dose—response thresholds in PbB from the onset of adverse health effects in terms of minimal amount of exposure assumed to produce such toxicity. 

Table 22.3 presents the full-spectrum of dose—toxic response relationships for lead toxicity in adults in terms of lowest reported adverse effect level thresholds. As with the earlier tables, only the lowest values for PbB in the associations specific for the indicated range are identified. It is also understood with these adult tabulations that as PbB values rise above lowest levels of determined associations, those toxic effects increase in severity and multiplicity. Toxicity criteria for reliability and validity parallel those enumerated for the earlier childhood tables. A number of dose-responses scaled to dose/exposure are identified in the table. In many cases, including hematotoxicity, peripheral neurotoxicity, and nephrotoxicity, effects are qualitatively similar but occur at higher empirically measured thresholds. 

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